1. Field of the Invention
The present invention relates to a monitor system including a monitor camera device and an image recording/reproducing device and in particular, to a technique for detecting failure of the monitor camera device.
2. Description of the Related Art
JP-A-9-74553 (Patent Document 1) is an example of the related art of the field of the invention. This invention has an object “to automatically detect imaging disturbance and take a countermeasure” and a solution as follows. “A system includes: a first monitor device 1 having a CPU 1, a ROM 2, a RAM 3, an operation processor 4, a frame memory 5, and a communication control unit 7 for imaging a monitor object by a monitor camera 6, compressing a still image of the monitor object, and transmitting it as image data; and a second monitor device 2 having a CPU 11, a ROM 12, a RAM 13, an operation processor 14, a frame memory 15, a display device 16, a communication control unit 17, and an alarm device 18 for receiving the image data from the first monitor device 1 inputted via a communication line 8, decompressing the image data to restore the still image of the monitor object, and displaying it to be monitored. If it is detected that a data amount of the image data obtained by compressing the image captured by the monitor camera 6 in the first monitor device 1 is smaller than a predetermined data amount, a message telling that something is wrong in imaging by the monitor camera 6 is displayed with alarm in the second monitor device.”